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May 7, 2006 -- People with lupus may be more likely to have a diminished sense of smell, a new study says.

The finding may be significant, Israeli researchers say, because a loss of smell could be a symptom that would help doctors make an earlier diagnosis of lupus and other diseases.

Olfactory dysfunction is known to exist in various central nervous system disorders, such as Parkinson’s disease, Alzheimer’s, schizophrenia, and multiple sclerosis.

The study, led by Yehuda Shoenfeld, MD, of Chaim Sheba Medical Center in Tel-Hashomer, Israel, involved 100 people, half of whom had systemic lupus erythematosus, or SLE, and half that did not have the disease. Lupus, an autoimmune disease, happens when the immune system attacks healthy tissues, causing inflammation, swelling, pain, and damage.

The researchers examined olfactory function (ability to smell) with three distinct “Sniffin Sticks” tests. In one, people were asked to identify a stick with an odor from sticks that had no smell. They also were tested to see if they could tell the difference between sticks of different smells. And the participants also were asked to identify a particular smell from among four options.

People with SLE showed significant olfactory dysfunction, compared to those in the control group, the researchers say. A greater proportion of SLE participants (46%) had decreased sense of smell compared to non-SLE participants (25%). Also, complete loss of smell was only seen in some SLE participants.

The study is published in the May issue of Arthritis & Rheumatism.

The study authors say that people with more active disease and past manifestations of the condition known as neuropsychiatric SLE or NPSLE had significantly lower total scores.

In a news release, the scientists say past research in mice has demonstrated a link between neuropsychiatric SLE and sense of smell.

Sense of smell is unfamiliar territory for rheumatologists and immunologists, but results from this and other studies demonstrate that an autoimmune mechanism may play a role in loss of smell, the researchers say.

Thus, “smell decrement has been found to be an early and predictive sign in several CNS [central nervous system] diseases, and therefore might be a useful and easy tool for the physician in early diagnosis of CNS involvement in autoimmune diseases.”